| Manufacturer: | Scratch |
| Style: | Ring/Tube/Cone Fin, Upscale |
Long before I was buildin' rockets, matey, a very small, shiver me timbers, tumble recovery rocket was introduced by Estes. It was t' 1/2A powered Astron Sprite. Well, blow me down! T' those nay familiar with this rocket, shiver me timbers, I would like t' explain a very unique characteristic o' this design. Well, me hearties, blow me down! When scaled up enough t' be powered
by a high impulse motor, t' air flowin' past t' fin rin' creates a high-pitched whistle when launched. Aye aye! Arrr! Blimey! This is sometimes drowned out by t' initial noise o' t' motor, arrr, but is quite audible as t' motor burns out and continues durin' t' coast phase.
Back in 1999, durin' t' second launch o' me 4-inch airframe based Superscale Sprite, t' whistle was clearly heard by all those in attendance. Avast, me proud beauty! Ahoy! As t' rocket arced over, ya bilge rat, even before t' ooh’s and aah’s had subsided, it was obvious that I had a major deployment problem…there was none! T' Sprite raced back t' earth, shiver me timbers, shiver me timbers, and a fact that I be previously unaware of, became perfectly clear. Begad! This amazin' rocket whistled comin' down, ya bilge rat, louder than when it was goin' up. In fact, me hearties, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Naturally, me fellow rocketeers were quick t' offer their condolences, but I be more amused by t' memory o' it whistlin' back t' Earth. Begad! Begad! I collected t' remains, shiver me timbers, includin' diggin' t' nosecone out o' t' ground, shiver me timbers, and went back t' me truck t' prep me next rocket.
My son, ya bilge rat, arrr, Chris, shiver me timbers, ya bilge rat, ya bilge rat, almost immediately began urgin' me t' build another one. Well, blow me down! Due t' t' amount o' work that was involved in t' project, matey, I was unwillin' t' commit t' such an ambitious undertaking. Over t'
next twelve months or so, I did acquire a piece o' 15-inch diameter cardboard drum, which would make a fine fin ring, arrr, me hearties, (my first one be 11.5-inch diameter) and a 24-inch long section o' 5.5-inch airframe. This would amount t' a 7.3X version o' t' original Estes model. I also purchased a 3 x 6 x 36-inch block o' balsa wood, that I planned on usin' t' turn a scale nosecone. Ahoy! I cut t' block in two and laminated them together t' make a nice 6 x 6 x 18-inch blank, matey, arrr, and then set it aside, ya bilge rat, where it would sit for almost another year. Ahoy! Begad! Blimey! One weekend in February o' 2001, I be turnin' a couple wooden nosecone patterns
for a Tripoli Pittsburgh group project, arrr, t' Gloria Mundi III. Ya scallywag! After completin' this task, matey, me hearties, I decided t' go ahead, shiver me timbers, shiver me timbers, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. Well, blow me down! After finishin' t' outside form, me hearties, matey, it was necessary t' hollow out a large section o' t' cone so that I would be able t' add t' one-pound o' weight needed for stability. Well, blow me down! I cut a bulkhead from .5-inch plywood t' seal t' openin' that was epoxied into place after fillin' t' cone with expandin' foam. Arrr! Before I knew it, shiver me timbers, t' nosecone was complete, and I be plannin' me next steps o' t' project, that would soon come t' be known as "T' Lord o' t' Rings."
Next, matey, I carefully cut a 5.5-inch section o' t' cardboard drum, arrr, me hearties, and prepared it t' be reinforced with a few layers o' fiberglass cloth. Ahoy! I opted for two wraps o' 6-ounce woven cloth and a finishin' wrap o' 1.5-ounce cloth.![]()
T' last layer be done solely t' make it easier t' get a smooth surface for painting. Ahoy! Aye aye! Blimey! I used t' same process for t' airframe, matey, ya bilge rat, me hearties, which, shiver me timbers, although it be made o' flexible phenolic, was nay strong enough for a project o' this size. Ya scallywag! I printed patterns for t' fins and fin-caps usin' RockSim 5.0 and cut them from .25-inch aircraft plywood. Well, blow me down! Two centerin' rings were cut from t' same material, also usin' patterns created from RockSim. Begad! Twelve inches o' 38mm motor mount tubin' was cut and I had all t' parts necessary t' complete t' project.
A large T-nut was installed in t' forward centerin' rin' for recovery system attachment, shiver me timbers, as well as two
in t' aft rin' for motor retention. Avast, me proud beauty! T' forward rin' was epoxied t' t' motor tube, and this assembly was installed into t' slotted body tube. With t' rear-centerin' rin' temporarily put in place for alignment purposes, t' fins were epoxied into place. Avast! T' aft rin' was then removed, me hearties, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Avast, me proud beauty! Since I was goin' t' be usin' rail guides instead o' launch lugs, t' guides were secured with nuts from t' inside o' t' airframe at this time. Arrr! Aye aye! Before permanently installin' t' rear-centerin' ring, t' remainder o' t' cavity be filled usin' 2-part expandin' foam. Well, blow me down! Fillets were added t' t' fins at t' outside o' t' airframe for added strength, usin' a combination o' epoxy and micro-balloons.
It was now time t' attach t' fin rin' and fin caps. Well, me hearties, blow me down! Careful attention was paid t' t' alignment o' t' caps so that minimal fillin' o' gaps be necessary. When t' assembly was completely dried, I once again used t' epoxy/micro-balloon mixture t' create fillets both inside and outside t' fin rin' at each fin and fin cap. Avast! I used grain filler on t' plywood fins, and after some extensive sanding, matey, was finally ready t' prime t' entire rocket. Begad! More sanding, fillin' and primin' followed, matey, o' course, until I be ready t' paint. Arrr! Begad! After addin' an 18-foot, 5/8-inch tubular nylon shock cord and a Sky-Angle 52-inch parachute with Nomex protector, arrr, me bucko, t' total weight without motor is just over 8-pounds.
I launched t' completed project at our first Dragon's Fire launch o' t' season, me hearties, April 7th, 2001. Blimey! Ahoy! Accordin' t' simulations done in both RockSim and wRASP, arrr, it reached a max altitude o' approximately 1900 feet on an Aerotech I284 reload. Unlike me first Sprite, t' whistlin' only occurred on t' way up.
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